The present invention pertains to a specialized, defensive coating, or coating structure, applicable to the outside of a fuel container, such as to the outside of a fuel tank or a fuel pipeline, to mitigate and fend off certain kinds of potential catastrophic fire and explosion events. More particularly, it relates to a plural-layer, plural-action (anti-fuel-leak, anti-shockwave, and additionally, with regard to one preferred embodiment, anti-fireball, and anti-“pool-fire”) protective coating for such a container.
To meet these objectives, the proposed coating possesses, differentially in its two, different, preferred embodiments, different overall category, plural, intentionally differentiated-defense, coating-layer features that are designed to guard specifically against container-attack-promoted, ignited-liquid-fuel contribution to, or initiation of, a catastrophic, consequential fire, and/or a container-explosion—such prospectively dangerous events resulting, for example, from an attack, such as a bullet or shrapnel penetration, or, respecting one of the preferred, added-protection embodiments of the invention, a close-by explosive weapon blast of the kind typically characterized by an initial, extremely high-pressure shock wave, followed almost immediately by an intense, blast-produced fireball, and thereafter by a high-heat-intensity, proximate “pool-fire” (a military term of art).
Threats of a consequential, fuel-container catastrophe triggered by container attacks such as those just mentioned are common potentials in military-action theaters, and similar threats, we have recognized in the conception and reduction to practice of the present invention, may also exist in other kinds of danger-prone situations.
In relation to these kinds of potential-catastrophe settings, an overall purpose of the present invention, accordingly, is to safeguard personnel and equipment from the harmful consequences of such attacks through minimizing, in several different ways which differentially address the different kinds of potential attacks, such as those kinds of attacks mentioned above, the likelihood of a successful, attack-induced, uncontrolled container rupture, container fuel leak, fuel ignition, and possible fuel-container explosion.
While there are disclosed herein several modified forms of the coating structure of the present invention, fundamentally there are two, key, or principal, preferred embodiments of the invention, one of which includes, and the other of which does not include, what is referred to herein as an intumescence-response layer. The presence or absence of this layer determines, for the respective, associated coating, the range of different defensive/protective options made available by the coating. With regard to these two principal embodiments, which, accordingly, form preferred embodiments for uses in somewhat different settings and applications as will be explained below, except for the presence or absence of an intumescence-response layer, in all other respects these two embodiments are substantially identical in construction. Modifications that are described regarding other facets of the invention are applied essentially equally to each of these two, different, key embodiments.
The present invention, in one of its preferred embodiments, and specifically that embodiment which offers the largest range of defenses to different, possible, container-attack problems, features a plural-layer, plural-action, protective coating for a liquid fuel-container, placeable adjacent the outside surface of such a container, designed to furnish differentiated defenses to attacks like those identified above—with this coating possessing:
(1) a self-sealing, anti-fuel-leakage, elastomeric-response layer having and inside face disposable directly and contactively adjacent such a liquid fuel container's outside surface, and an outside face spaced from its inside face;
(2) an intumescence-response layer having an inside face disposed operatively adjacent the outside face in the elastomeric-response layer, formed of an intumescence putty material, and having an outside face; and
(3) a packetized, burst-reactive, flame-suppression layer including plural, side-by-side-adjacent, independently burst-reactive packets each containing, burst-releasably, a powdered, flame-suppression agent, these packets collectively defining an inner side for the flame-suppression layer disposed adjacent the intumescence-response layer's outside face.
Preferably, the burst-reactive packets are generally planar, flexible, characterized with hexagonal perimeters having packet edges, and disposed in an appropriate, side-by-side tiled, and hexagonal packet-edge adjacency fashion, in the flame-suppression layer. As will be explained, each of these packets is formed herein from a stacked arrangement of plural, relatively thin but same perimetral outline, subpackets fundamentally made of what is known in the art as a very flexible, three-dimensional spatial fabric material—this material being defined, per se, by a pair of spaced, facial fabric sheets that are interconnected by a tangled collection of slender, nonlinear, wandering fibres which meander in and through a surrounding void space extant between the spatial-fabric facial sheets. Stacking of these subpackets conveniently accommodates construction of a flexible, assembled hexagonal, or hex, packet having the desired overall thickness.
Uniquely with respect to the packetized construction of the flame-suppression layer, if damage occurs to a packet, or packets, in this layer, as, for example, by an inadvertent contact-breakage of one or more packet(s), or by a projectile penetration, or penetrations, the damaged packet(s) may easily be replaced so as to “repair” the functional integrity of the layer for its intended defensive purpose.
The self-sealing, anti-fuel-leakage, elastomeric-response layer employed is plural-sublayer in nature, and includes inner, intermediate and outer sublayers each formed, commonly, with a main body of a high-elastomeric, liquid-fuel-reactive material, with an augmentation included in the intermediate sublayer in the form of a population of plural, distributed, liquid-fuel-imbiber beads embedded in the intermediate sublayer's main, high-elastomeric body.
Also included in this embodiment of the invention, as well as in all other embodiments and applications wherein the outermost, protective layer takes the form of the mentioned, packetized, burst-reactive flame-suppression layer, is a relatively thin (typically with a thickness lying in the range extending from about 0.06- to about 0.08-inches), appropriately sprayed-on, surrounding “capture jacket” of the same high-elastomeric material which has been mentioned above herein, applied over the packets in the flame-suppression layer to stabilize their attachments (contact adhesive bonds) to the immediately underlying coating protective layer.
According to one modified form of the invention, the proposed coating includes yet another, extra, anti-fuel-leakage, protective layer which is disposed as an overall, outside layer applied to surround all of the other layers in the coating—this extra, outer layer being like the “more internal”, plural-sublayer, liquid-fuel-reactive, high-elastomeric material layer mentioned above.
The other, principal, preferred embodiment of the invention, and specifically that embodiment which offers a somewhat reduced range of defenses to different, potential, container-attack problems, also features, generally speaking, a plural-layer, plural-action, protective coating for a liquid fuel-container, placeable adjacent the outside surface of such a container, designed to furnish differentiated defenses to certain ones of the attacks identified above—this coating embodiment lacking an intumescence-response layer, but nonetheless possessing:
(1) a self-sealing, anti-fuel-leakage, elastomeric-response layer having an inside face disposable directly and contactively adjacent such a liquid fuel container's outside surface, and an outside face spaced from its inside face; and
(2) a packetized, burst-reactive, flame-suppression layer including plural, side-by-side-adjacent, independently burst-reactive packets, each containing, burst-releasably, a powdered, flame-suppression agent these packets collectively defining an inner side for the flame-suppression layer disposed adjacent the elastomeric response layer's outside face.
As mentioned earlier, this embodiment of the invention differs from the first, above-described, principal embodiment only by the absence in it of the intumescence-response layer. It is especially useful in applications wherein both minimizing coating weight is important, and there is little anticipated threat of a “pool-fire” incident, or the like.
Regarding all forms of the invention, included among the materials that are preferably employed herein to form the different layers in the proposed coating are (1) a high-elastomeric, liquid-fuel reactive elastomer material (as mentioned above), (2) liquid-fuel-imbiber beads, (3) an intumescence putty material, (4) a three-dimensional spatial fabric, and (5), a powdered, flame-suppression agent. While there are various commercially available offerings of very adequate choices for such materials, we have selected the following, specific, respective materials which have been found to perform admirably in the coating of the present invention.
The liquid-fuel-reactive, high-elastomeric material employed herein takes the form of a two-component polyurethane elastomer product sold under the trademark TUFF STUFF® FR (with the letters FR standing for fire-resistant), made by Rhino Linings USA, Inc.—a company based in San Diego, Calif. This material, which is preferably sprayed into place, and which plays a key role in furnishing self-sealing, anti-fuel-leakage behavior in the coating of the invention, in addition to responding to, say, a bullet puncture wound with high-elastomericity wound-closure action, additionally reacts to contact with hydrocarbon fuel—imbibing such fuel, and swelling in the process to aid in wound closure performance. In relation to elastomericity, it exhibits an elasticity which permits an elastic elongation before “breakage” of about 400%, has a tensile strength of about 1700-1900-psi, and possesses a tear resistance of about 140-150-pli.
More information about this material, about how it may be applied and employed, and about how it responds/reacts to contact with leakage fuel coming from a puncture wound in an associated, protected fuel container, will be found in U.S. Pat. No. 7,169,452, the full disclosure content in which is hereby incorporated herein by reference
The liquid-fuel-imbiber beads used herein preferably take the form of the imbiber-bead product known as IMB230300, made by Imbibitive Technologies America, Inc. in Midland, Mich. These beads have a strong affinity for rapidly absorbing (imbibing) hydrocarbon fuel, and they swell significantly and quickly in volume as a consequence—an action which cooperates with the surrounding, embedding, high-elastomer material in aid of speedy and definitive puncture-wound, anti-fuel-leakage closure. These beads preferably are blended in any appropriate manner into the entraining/embedding elastomer material to constitute about 20% by weight in the combined material.
The intumescence-response layer, when included in the overall defensive coating/layer structure of the invention, takes the form of any suitably, conventionally available, easily layer-applied, intumescence putty material. Many such conventional putty materials, all of which are entirely appropriate for use in the coating structure of the present invention, are readily commercially available. A good representative, intumescence putty product which we have found to be very satisfactory is one made by 3M, identified as 3M™ Fire Barrier Moldable Putty Pads MPP+ (Product Number MPP+4X8).
This intumescence putty material, as is understood by those generally skilled in the art, functions, in the presence of external heat, i.e., in the presence of a high-temperature, ambient condition such as that produced by a proximate, external fire, to swell with a kind of popcorn-like, popping action which releases water vapor in a manner which helps to isolate and protect, for a relatively long period of time, the protected, container-contained fuel from a dangerous temperature rise and potential fuel ignition/explosion. Preferably, the intumescence putty material is applied to form the intumescence-response layer in a fashion whereby it is captured, and stabilized by an embedded, open mesh fabric possessing open meshes, typically of about ½-inches in mesh size, made of a high-temperature, fibre/strand material, such as basalt. This mesh fabric is not specifically presented in the drawings herein in order to minimize unnecessary drawing clutter.
Regarding the burst-reactive, flame-suppression layer, a preferred three-dimensional fabric which is usable very effectively in the coating structure of the present invention to form the hexagonal packets mentioned above is a product made by Gehring Textile, Inc., Garden City, N.Y.—this product being identified as Product (or Part) #SHR705/60, Black, No. 9321. Various details of these packets will be discussed below, and as will be further explained, each packet employed herein is actually formed as an assembly with a user-selected plurality of facially-contact-adhesively bonded, generally planar, hexagonal subpackets, each with a thickness of about ¼-inches (see D2 in FIG. 3). Preferred overall thickness of a “packet assembly of subpackets” lies in the range of about ½- to about 1-inches, and a 1-inch thickness, generally a good selection for many applications, is specifically chosen for illustration herein.
Each hexagonal packet herein has a dimension (measured between opposite, straight-linear sides, referred to herein as hexagonal packet edges) of about 6-inches (see D1 in FIG. 2), and the hexagonal perimetral outlines of these packets readily and conveniently allow them to be placed in a grouped, hexagonally tiled fashion around the outside surface of a container in a manner readily accommodating different kinds of surface curvatures in a container.
The void spaces present in the individual hexagonal subpackets, as will further be explained below, are densely filled with a conventional, dry-chemical flame-suppression agent, such filling being performed herein conveniently via a gravity-filling technique through a not-yet-closed packet edge which has been purposely left open for this purpose. The agent used may be of any suitable type currently employed in dry-powder fire extinguishers, and the agent which we have specifically selected is the one known in the relevant art as Purple K. Purple K is currently considered to be the most effective dry chemical in fighting Class B (flammable liquid) fires, and can be used against some energized electrical equipment fires (USA Class C fires). It has about 4-5 times more effectiveness against class B fires than carbon dioxide, and more than twice that of sodium bicarbonate. Dry chemical powder works by directly inhibiting the chemical chain reaction which forms one of the four sides of the fire tetrahedron (Heat+Oxygen+Fuel+Chemical Chain Reaction=Fire). To a much smaller degree, a dry-powder agent also has a smothering effect which excludes oxygen from a fire.
The Purple-K powder agent is free-flowing, floatable on most liquids, non-abrasive, and does not wet with water. It has violet color, to distinguish it from other dry agents. Its principal component is potassium bicarbonate (78-82% by weight), with addition of sodium bicarbonate (12-15%), mica (1-3%), Fuller's earth (1-3%), amorphous silica (0.2-%), and is made hydrophobic by methyl hydrogen polysiloxane (0.2-1%).
In the structure of the present invention, the layers of the proposed protective coating coact effectively with one another in important ways, both independently and interdependently, to offer appreciable defenses against the kinds of dangerous events mentioned above. These differentiated-functionality protective layers, while cooperative both independently and interdependently, importantly are not cross-disabling relative to one another in many instances, in the sense that “defensive activation” of one in an intended, related defense mode, will not disable the still-defensive “posture” of the other layers.
The above-mentioned and other features and advantages that are offered by the invention will become more readily apparent and fully appreciated as the detailed description of the invention which follows below is read in conjunction with the accompanying drawings.
To be noted at this point is the fact, that the structural components pictured in the above-described drawing figures are not drawn to scale.